diff --git a/src/sms.gd b/src/sms.gd
index 1754e88..83693ca 100644
--- a/src/sms.gd
+++ b/src/sms.gd
@@ -56,7 +56,10 @@ func add_scene(sname: String, sclass: Node, type: CoreTypes.SceneType) -> bool:
 	logger.verbf("sms", "Adding scene \"" + sname + "\" of type " + str(type))
 	if exists(sname) != CoreTypes.SceneType.NONE:
 		logger.errorf("sms", "Scene with name \"" + sname + "\" already exists")
-		return true
+		return false
+	if typeof(sclass) != TYPE_OBJECT or !sclass.is_class("Node"):
+		logger.errorf("sms", "Scene class \"" + sname + "\" is not of type Node"
+		return false
 	sclass.name = sname
 	match(type):
 		CoreTypes.SceneType.DEBUG: scenes_debug.add_child(sclass)